Plastic bottles

ABSTRACT

Plastic bottles ( 1 ) which are characterized in that: they are composed of neck ( 2 ), shoulder ( 3 ), body ( 4 ) and bottom ( 5 ); the cross-sectional shape at the body ( 3 ) is a regular polygon, the number of angles of which is an even number of not less than 4 nor more than 32; each angle of the polygon is rounded off by an arc ( 8 ) whose radius is not longer than half the radius of a circle circumscribed about the cross-sectional shape at body ( 3 ); cross-sectional shapes have the same shape at any portion of body ( 3 ); circles circumscribed about the cross-sectional shapes are identical with one another; the circumscribed circles have a center on the vertical central axis of body ( 3 ); and the cross-sectional shape of body ( 3 ) rotates around said central axis in proportion to height along said central axis.

TECHNICAL FIELD

This invention relates to plastic bottles to be used as liquidcontainers, more specifically to plastic bottles for beverages which areto be hot-filled or aseptic-filled.

BACKGROUND ART

Biaxially stretched blow-molded bottles made from polyethyleneterephthalate (PET) are widely used as beverage containers. Containersare usually filled with beverage product either by hot-filling or byaseptic-filling. In hot-filling, biaxially stretched blow-moldedcontainers are filled with beverage which has been heated to around 90°C., sealed with a cap, and are then cooled. In aseptic-filling,containers are sterilized, and are then filled in the resultant asepticenvironment. Hot-filling has been accompanied with a problem thatcontainers expand when filled or capped, and that, when cooled,containers shrink due to reduced pressure inside. Also aseptic-fillinghas had a problem that containers shrink due to reduced pressure whichis caused by the contents' absorbing oxygen in the head space.

In recent years, these PET bottles are often displayed in a warmedshowcase. This causes a problem that containers swell due to increasedinternal pressure when warmed.

As a solution to the above-mentioned problems, bottles are usuallyprovided, on their body, with an absorption panel or concave ribs whichswell when the bottle expands and shrink when the bottle isdecompressed, and thus absorb deformation. In another solution, theamount of material resin is increased by which to enhance the rigidityof bottles. These approaches require a large absorption panel, whichcompromises the appearance of bottle. Also from the viewpoint of overalldesign, these bottles lack continuity in outline, and therefore lookawkward.

In addition, absorption panels have a concave-convex shape. Hence, whenshrink-label is put on bottle for surface decoration, gaps can be madebetween the bottle and the shrink-label to cause a problem that bottlebecomes difficult to handle, that shrink-label is torn duringtransportation, and that moisture which has been trapped in these gapsis difficult to be removed.

If no heat insulation panel is used so that the bottle may have acylindrical shape by which to avoid the above-mentioned problems,bottles shrink unevenly when decompressed, compromising theirappearance. Besides, if the amount of material resin of bottle isreduced, longitudinal buckling strength is decreased, and, therefore,bottles crush when stacked. Due to these problems, the only realisticway to make bottles withstand decompression has been to increase theamount of material resin of bottle, which is undesirable from theviewpoint of productivity and economy.

Another possible solution is a polygonal bottle as shown in JapaneseDesign Registration No. 935840. This solution has a problem that bottlesof this shape has low strength due to the lack of heat insulation panel.Hence, each face which constitutes side wall is deflected in verticaldirection under reduced pressure, resulting in conspicuous deformation.Otherwise, portions with a small wall-thickness give way under reducedpressure, and, thus, only the faces of those portions are buckled toexhibit remarkable deformation.

In the bottles as shown in Japanese Design Registration No. 961967,triangular faces are arranged geometrically and on upper and lower partsof twisted wall, which structure serves to give strong bottles. Besides,vertical section (side wall) has a terraced shape with a recession,which also contributes to strength. Each of the twisted side facesresists deformation as a result of the above-mentioned structure, whichalso serves to strengthen the bottle. Hence, the shape of bottle asdisclosed in Japanese Design Registration No. 961967 is appropriatelydesigned to increase bottle strength (enhance the rigidity ofcontainer). When reduced pressure is applied to bottle, however, highrigidity may give rise to buckling in thin areas alone, which leads tosevere deformation. Furthermore, since vertical section has a terracedshape where triangular faces are complicatedly arranged, there is aconcern that, in an sterilization step of aseptic filling, the flow ofsterilizing liquid may be insufficient in some areas, or that the liquidmay be incompletely rinsed away.

Moreover, the shape of bottles has so far been restricted to stereotypesuch as cylindrical or square to ensure fast and reliable feeding ofbottles on beverage production lines, and especially to ensure thatbottles do not tumble down when slid and fed on continuous productionlines, and also to make it easy to pack bottles neatly in casers.

DISCLOSURE OF INVENTION

In order to resolve the above-mentioned problems with conventionalbottles, this invention is to provide, at a low price, plastic beveragebottles which, in aseptic-filling and hot-filling, are not deformedawkwardly by the change in internal pressure which is caused by warmingor cooling, are capable of absorbing decompressed volume, are sowell-designed as to avoid poor appearance, and are easy for consumers tohandle, free from tearing or peeling of shrink-labels duringtransportation, have high load capacity strength and horizontalcompression strength as well as package strength, and bring no problemin bottle-filling line.

To satisfy the above-mentioned objective, the plastic bottles of thisinvention are characterized in that: they are composed of neck,shoulder, body and bottom; the cross-sectional shape at the body is aregular polygon, whose angles have an even number of not less than 4 normore than 32; each angle of the polygon is rounded off by an arc whoseradius is not longer than half the radius of a circle circumscribedabout the cross-sectional shape at body; cross-sectional shapes are thesame at any portion of body; circles circumscribed about thecross-sectional shapes are identical with one another; the circumscribedcircles have a center on the vertical central axis of body; and thecross-sectional shape of body rotates around said central axis inproportion to height along said central axis.

In a preferred embodiment of the above-mentioned plastic bottles, thecross-section of body rotates to make a rotation angle of 360°/thenumber of angles in the polygon.

In another preferred embodiment of the above-mentioned plastic bottles,cross-section at shoulder is also a polygon wherein each angle thereofis rounded off by a circular arc, and said cross-section does notrotate.

In another preferred embodiment of the above-mentioned plastic bottles,the plastic bottle is made from polyethylene terephthalate, and ismolded by biaxial stretch blow molding.

A bottle which has been manufactured under these conditions has awall-side of a shape of twisted regular polyhedron from bottom toshoulder. When this container is decompressed, each face is decompressedwhile the container as a whole neutralizes deformation caused by thedecompression, in the direction of the twist. Thus, although deformationtakes place, it is not conspicuous as compared with the shape ofcontainer before deformation. With regard to strength of resistance todecompression induced by deformation, the bottle deforms as a whole sothat deformation may be neutralized, and, therefore, remarkabledeformation such as so-called buckling is hard to occur. Thus, thebottle of this invention can be said to be stronger againstdecompression than conventional bottles, in view of the concept of“remarkable deformation which affects the acceptability of products”. Itmay be said that the bottle of this invention breathes in accordancewith change in internal pressure. It has been confirmed that, on theafore-mentioned accounts, even though severe deformation like bucklingoccurs, the bottle returns to the original shape as soon asdecompression is eased, unlike conventional bottles reinforced withpanels that do not return to their original shapes.

This invention provides plastic beverage bottles which, inaseptic-filling and hot-filling, are not deformed awkwardly by thechange in internal pressure which is caused by warming or cooling, areso well-designed as to avoid poor appearance, and are easy for consumersto handle, free from peeling of shrink-labels during transportation,have high load capacity strength, and bring no problem in bottle-fillingline.

In conventional plastic bottles, when internal pressure changes, centralaxis of neck section leans out of the central axis of body of thebottle, and, thus, deformation occurs. In the bottle of this invention,plural numbers of helixes are wound tighter around the body, with theresult that the height of plastic bottle decreases, and, accordingly,volume is decreased. Or, on the contrary, plural numbers of helixes arewound more loosely, with the result that the height of plasticincreases, and, accordingly, volume is increased. Such deformationprevents the plastic bottle of this invention from deforming in such away that the central axis of its neck section leans out of central axisof body section.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1: Schematic drawing of an embodiment of this invention

FIG. 2: Cross-section of the body of bottle of an embodiment of theinvention

FIG. 3: Cross-section of the body of bottle of an embodiment of theinvention

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates an embodiment of this invention. The plastic bottle(1) of this invention is comprised of neck (2), shoulder (3), body (4),and bottom (5), and the bottle (1) is to be sealed with a closure (6).As closure (6), anything can be acceptable so long as it ensures asecure seal. Examples of closures include screw caps, push caps, andheat-sealing, among which screw cap is preferable in view of re-cappingafter opened.

As the material of plastic bottle, polypropylene, polyethylene,polyamide, polyethylene terephthalate, and laminate thereof arethinkable. Anything of these is allowable so long as it is capable offorming a desired bottle shape. In view of use for beverage, biaxiallystretched blow-molded bottles made from polyethylene terephthalate arepreferable.

Cross section (7) at the body of this plastic bottle (1) is regularpolygon, wherein each angle is rounded off by arc (8). Any section hasthe same shape between the lower end (9) and the top end (10) of thebody of plastic bottle. Owing to this feature, no concave is made on thebody. Hence, when shrink label is placed as a surface decoration, thereis made no gap between the bottle and the label, and, thus, label isprevented from peeled or torn during distribution, and, moreover, wateris prevented from collecting between the bottle and the label. Theabsence of gap between the shrink label and the bottle gives consumers abetter handling.

The bottle of this invention is further characterized in that any circle(11) circumscribed about the cross-section at the body has the sameshape, and that the centers (12) of such circumscribed circles areplaced on the same axis.

The number of angles of the regular polygon is preferably an even numberbetween four and 32. If the number of angles is more than 32, theexternal shape becomes indistinguishable from that of a cylindricalbottle. Six or eight is desirable from the viewpoint of designing. Ifthe number of angles is odd, wall thickness becomes non-uniform whenbottle is blown-up. Furthermore, split line of blow-mold may becomecomplicated, and scratch may occur when bottle is taken out of the mold.

Each angle of the polygon at body is rounded off by a circular arc (8)whose radius is not longer than half the radius of a circle (11)circumscribed about the cross-section of the body. This feature not onlyleads to excellent design, serving to give a beautiful expression ofpolygonal surfaces, but also produces ribbing effects when the radius ofarc (8) is small, which effects enhance resistance to vertical loading.

Any section has the same shape between the lower end (9) and the top end(10) of the body of plastic bottle. Furthermore, any circle (11)circumscribed about the cross-section at the body has the same shape,and the centers (12) of such circumscribed circles are placed on thesame axis. Owing to these features, bottles are less likely to becomejammed on the production line.

Cross-section at the body is rotated around the center (12) of circlecircumscribed about the cross-section at the body, and in proportion toheight. This feature achieves flowing outline together with improvedresistance to horizontal load. Due to this rotation, contact surfaces ofbottle come near to circular shape, which improves rolling property.This also makes it easy to charge a vending machine with bottles.

Also with regard to change in internal volume which has been a technicalproblem, bottles are expanded or contracted in vertical direction owingto rotation, and are thus allowed to deform without damaging appearance.As for the relation between angle of the rotation of cross-sectionalshape at body and height, it is preferably 0.6°/mm or less, or, moredesirably, 360°/number of angles. When rotation angle is too large inrelation to height, the undercut of mold becomes large, which causes aproblem that it becomes difficult to draw bottles from the mold in blowmolding, and that scratches occur when bottles are drawn from mold. Whenthe rotation angle is 360°/number of angles, there occurs no problem ofundercut, and bottles are molded without any problem.

With respect to bottle design, also cross-sectional shape at shouldermay be a polygon whose angles are each rounded off by an arc, for thepurpose of emphasizing the streamline image much more. In that case, itis preferable not to rotate the cross-sectional shape so as to avoidundercut problem.

EXAMPLE

An embodiment of the above-mentioned invention is explained by a workingexample as follows.

A bottle was manufactured by biaxial stretching blow-molding with use ofpolyethylene terephthalate. Material resin was used in an amount of 29g, capacity was 500 ml, maximum diameter was 67 mm, and height was 207mm. The bottle was composed of neck, shoulder, body and bottom. Thecross-sectional shape at the body was a regular hexagon. Each angle ofthe regular hexagon was rounded off with an arc. Cross-sections had thesame shape at any portion of body. Circles circumscribed about the crosssectional shape were identical. The centers of the circumscribed circleswere on the same axis. The circumscribed circle had a radius of 33.5 mm.The arc had a radius of 5 mm.

Cross sectional shape at body was rotated uniformly at a rate of 0.4°/mmaround the center, as axis, of circles circumscribed about said crosssectional shape. Total rotation angle was 60 degrees. Also at shoulder,cross sectional shape was a regular hexagon, where each angle wasrounded off with an arc. The cross sectional shape was not rotated.

The bottles as designed above had good acceptability, and had good“handleability” as well. After hot-pack filled and then cooled, thebottles caused no problem in production-line suitability. The bottlesmaintained acceptable appearance. When subjected to a transportationtest, the bottles caused neither peeling of labels, nor buckling underloading.

INDUSTRIAL APPLICABILITY

The plastic bottles of this invention are usable as containers forbeverages on the market.

1. Plastic bottles which are characterized in that: they are composed ofa neck, a shoulder, a body and a bottom; a cross-sectional shape at thebody is a regular polygon, the number of angles of which is an evennumber of not less than 4 nor more than 32; each angle of the polygon isrounded off by an arc whose radius is not longer than half the radius ofa circle circumscribed about the cross-sectional shape at the body; thecross-sectional shapes have the same shape at any portion of the body;the circles circumscribed about the cross-sectional shapes are identicalwith one another; the circumscribed circles have a center on thevertical central axis of the body; and the cross-sectional shape of thebody rotates around said central axis in proportion to a height alongsaid central axis.
 2. Plastic bottles of claim 1 wherein thecross-sectional shape at the body rotates, the relation between rotationangle and height being 1°/mm or less.
 3. Plastic bottles of claim 1wherein the cross-sectional shape at the body rotates to make a rotationangle of 360°/the number of angles in the polygon.
 4. Plastic bottles ofclaim 1 wherein also the cross-sectional shape at the shoulder is apolygon whose angles are each rounded off by an arc, and wherein thecross-sectional shape is not rotated.
 5. Plastic bottles of claim 1which are made from plyethylene terephthalate, and have been molded bybiaxial stretch blow-molding.